People are increasingly utilizing portable computing devices to perform various types of tasks. Accordingly, there is a desire to increase the ways in which users can interact with the devices to perform these tasks. One interaction approach includes providing users with automatic and/or personalized services upon determining the presence of or upon recognizing the face of a user based on a digital image showing a front view of the user's face. In order to achieve this, however, a camera of the computing device must periodically capture images of an environment and process these images to determine whether a user is present therein. Such approaches can be computationally expensive, particularly for portable computing devices that have limited processing capability and/or limited battery life, which can be significantly drained by unnecessary image capture and processing. Accordingly, a less computationally expensive way for determine when to perform object detection is desirable.